I can start the standalone program and choose to disable certain rules categories and load my own rule xml file. I can choose to run this as a server in the options. However, this is only accessible to localhost clients. Then I turn to bring up a HTTP server instance with the commandline and a "public" argument. It works fine but I can't disable the built-in rules. How can I tell the server program to disable certain rule categories?Many thanks!

You can use the --config option to specify a properties file. This file again can then point to a configuration file using rulesFile=/path/to/.languagetool.cfg. .languagetool.cfg can then contain information about rules that are turned off (you can simply use the configuration file that LT writes anyway when you make changes to the configuration in the user interface).